#include <string.h>
#include <stdlib.h>
#include <stdio.h>
#include <signal.h>
#include <arpa/inet.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <unistd.h>
#include <netinet/in.h>
#include <netinet/ip.h>
#include <netinet/ip_icmp.h>
#include <netdb.h>
#include <setjmp.h>
#include <errno.h>
#include <sys/time.h>

#include "ping.h"

#define PACKET_SIZE 4096
#define MAX_WAIT_TIME 5
#define MAX_NO_PACKETS 3
#define _DEBUG_ 1
#define OFF_LINE 1
#define ON_LINE 0

char sendpacket[PACKET_SIZE];
char recvpacket[PACKET_SIZE];
struct sockaddr_in dest_addr;
struct sockaddr_in from;
struct timeval tvrecv;
pid_t pid;
int sockfd, datalen = 8;
int nsend = 0, nreceived = 0;
void tv_sub(struct timeval *out,struct timeval *in);



void statistics(int signo)
{
    //printf("\n--------------------PING statistics-------------------\n");
    //printf("%d packets transmitted, %d received , %%%d lost\n", nsend, nreceived, (nsend-nreceived)/nsend*100);
    close(sockfd);
    //exit(1);
}

/*校验和算法*/
unsigned short cal_chksum(unsigned short *addr,int len)
{
    int nleft = len;
    int sum = 0;
    unsigned short *w = addr;
    unsigned short answer = 0;

    /*把ICMP报头二进制数据以2字节为单位累加起来*/
    while (nleft > 1){
        sum += *w++;
        nleft -= 2;
    }
    /*若ICMP报头为奇数个字节，会剩下最后一字节。把最后一个字节视为一个2字节数据的低字节，这个2字节数据的高字节为0，继续累加*/
    if (nleft == 1){
       //*(unsigned char *)(&answer)=*(unsigned char *)w;

       //answer = (*(unsigned char *)w) << 8;

       //printf("answer = %x\n", answer);

      sum += *(unsigned char *)w;
      //printf("sum = %x\n", sum);
    }
    sum = (sum>>16) + (sum&0xffff);
    sum += (sum>>16);
    answer =~ sum;

    return answer;
}

/*设置ICMP报头*/
int pack(int pack_no)
{
    int packsize;
    struct icmp *icmp;
    struct timeval *tval;

    icmp = (struct icmp*)sendpacket;
    icmp->icmp_type = ICMP_ECHO;
    icmp->icmp_code = 0;
    icmp->icmp_cksum = 0;
    icmp->icmp_seq = pack_no;
    icmp->icmp_id = pid;
    packsize = 8 + datalen;
    tval = (struct timeval *)icmp->icmp_data;
    gettimeofday(tval, NULL); /*记录发送时间*/
    #if _DEBUG_
    //printf("sec = %ld, usec = %ld\n", tval->tv_sec, tval->tv_usec);

    #endif
    icmp->icmp_cksum = cal_chksum( (unsigned short *)icmp,packsize); /*校验算法*/
    #if _DEBUG_
       //printf("cksum = 0x%x\n", icmp->icmp_cksum);
    #endif
    return packsize;
}

/*发送三个ICMP报文*/
void send_packet()
{
    int packetsize;

    {
        nsend++;
        packetsize = pack(nsend); /*设置ICMP报头*/
        #if _DEBUG_
        //printf("nsend = %d, packetsize = %d\n", nsend, packetsize);

        #endif
        if (sendto(sockfd, sendpacket, packetsize, 0,
        (struct sockaddr *)&dest_addr, sizeof(dest_addr)) < 0){
            //perror("sendto error");
            return;
        }
        //usleep(1000); /*每隔一秒发送一个ICMP报文*/

    }
}

/*接收所有ICMP报文*/
void recv_packet()
{
    int n, count = 0;
    socklen_t fromlen;
    extern int errno;

    //fromlen = sizeof(from);

    while ( count < 2){
        count++;
        fromlen = sizeof(from);
        alarm(MAX_WAIT_TIME);
        if ((n = recvfrom(sockfd, recvpacket, sizeof(recvpacket), 0,
        (struct sockaddr *)&from, &fromlen)) < 0){
            if (errno == EINTR){
              //printf("errno == EINTR\n");
              continue;
            }
            //perror("recvfrom error");
            continue;
         }
         alarm(0);
         //printf("n = %d\n", n);
         //gettimeofday(&tvrecv, NULL); /*记录接收时间*/

        if (unpack(recvpacket, n) == -1) continue;
        nreceived++;
        break;
    }

    return;
}
/*剥去ICMP报头*/
int unpack(char *buf,int len)
{
    int iphdrlen;
    struct ip *ip;
    struct icmp *icmp;
    struct timeval *tvsend;
    double rtt;

    ip = (struct ip *)buf;
    iphdrlen = ip->ip_hl<<2; /* ip_hl is the words of ip header*/
    icmp = (struct icmp *)(buf+iphdrlen); /*越过ip报头,指向ICMP报头*/
    len -= iphdrlen; /*ICMP报头及ICMP数据报的总长度*/
    if (len < 8) /*小于ICMP报头长度则不合理*/
     {
        //printf("ICMP packets\'s length is less than 8\n");
        return -1;
     }
     /*确保所接收的是我所发的的ICMP的回应*/
     //printf("%d, icmp_id = %d\n", ICMP_ECHOREPLY, icmp->icmp_id);

     if ((icmp->icmp_type == ICMP_ECHOREPLY) && (icmp->icmp_id == pid)){
         gettimeofday(&tvrecv, NULL);
         #if _DEBUG_
         //printf("sec = %ld, usec = %ld\n", tvrecv.tv_sec, tvrecv.tv_usec);

         #endif
         tvsend = (struct timeval *)icmp->icmp_data;
         tv_sub(&tvrecv, tvsend); /*接收和发送的时间差*/
         rtt = tvrecv.tv_sec*1000 + (double)tvrecv.tv_usec/1000; /*以毫秒为单位计算rtt*/
         /*显示相关信息*/
         /*printf("%d byte from %s: icmp_seq=%u ttl=%d rtt=%.3f ms\n",
         len, inet_ntoa(from.sin_addr), icmp->icmp_seq, ip->ip_ttl, rtt);*/
         return 1;
     }
     else return -1;
}


int check_on_line(char *argv)
{
    struct hostent *host;
    struct protoent *protocol;
    unsigned long inaddr = 0l;
    //int waittime = MAX_WAIT_TIME;

    memset(sendpacket, 'a', sizeof(sendpacket));
    int size = 50*1024;


    if ((protocol = getprotobyname("icmp")) == NULL){
        perror("getprotobyname");
        exit(1);
    }
    /*生成使用ICMP的原始套接字,这种套接字只有root才能生成*/
    #if _DEBUG_
    //printf("the protocol number used is %d\n", protocol->p_proto);
    #endif
    if ((sockfd = socket(AF_INET, SOCK_RAW, protocol->p_proto)) < 0){
        perror("socket error");
        exit(1);
    }
    /* 回收root权限,设置当前用户权限*/
    //setuid(getuid());

    /*扩大套接字接收缓冲区到50K这样做主要为了减小接收缓冲区溢出的
      的可能性,若无意中ping一个广播地址或多播地址,将会引来大量应答*/
    setsockopt(sockfd, SOL_SOCKET, SO_RCVBUF, &size, sizeof(size));
    bzero(&dest_addr,sizeof(dest_addr));
    dest_addr.sin_family = AF_INET;

    /*判断是主机名还是ip地址*/
    if ((inaddr = inet_addr(argv)) == INADDR_NONE){
       if ((host = gethostbyname(argv)) == NULL) /*是主机名*/
       {
          perror("gethostbyname error");
          exit(1);
       }
       memcpy( (char *)&dest_addr.sin_addr, host->h_addr, host->h_length);
    }
    else /*是ip地址*/
    {
      memcpy( (char *)&dest_addr.sin_addr.s_addr, (char *)&inaddr, sizeof(inaddr));
    }
    /*获取main的进程id,用于设置ICMP的标志符*/
    pid = getpid();
    /*
    printf("PING %s(%s): %d bytes data in ICMP packets.\n",argv,
    inet_ntoa(dest_addr.sin_addr),datalen);*/


    signal(SIGALRM, statistics);
    while (nsend < MAX_NO_PACKETS)
    {
       send_packet(); /*发送所有ICMP报文*/
       recv_packet(); /*接收所有ICMP报文*/
       sleep(1);
    }
    statistics(SIGALRM);
    if(0 != nreceived){
        nsend = 0;
        nreceived = 0;
	    return ON_LINE;
    }
    else{
        nsend = 0;
        nreceived = 0;
	    return OFF_LINE;
    }
}
/*两个timeval结构相减*/
void tv_sub(struct timeval *out, struct timeval *in)
{
    if ((out->tv_usec -= in->tv_usec) < 0){
        --out->tv_sec;
       out->tv_usec += 1000000;
    }
    out->tv_sec -= in->tv_sec;
}
/*
int
main(void)
{
    int res;
    res = check_on_line("10.14.2.40");
    printf("res: %d\n", res);
    return 0;
}*/
